# example8_16.py

'''
>>> import weakref
>>> s1 = {1, 2, 3}
>>> s2 = s1
>>> def bye():
...     print('Gone with the wind...')
...
>>> ender = weakref.finalize(s1, bye)
>>> ender.alive
True
>>> del s1
>>> ender.alive
True
>>> s2 = 'spam'
Gone with the wind...
>>> ender.alive
False
'''
